DIRECTOR 黃明東 主治醫師 SENIOR CLERK 詹家榮 17, FEB., 2009 國考班 – Rotator cuff tear

Case A 63-year-old woman goes to her primary care physician complaining that, since falling on her outstretched hands 3 weeks ago, she can no longer use her right arm to remove books from the overhead shelves in her office. Further questioning reveals that she also has pain in her right shoulder at night that occasionally wakes her up, and that she now avoids sleeping on her right side. Physical examination reveals tenderness to palpation below the right acromion; also, the patient has pain at 60° as she abducts her right arm, and is unable to abduct with resistance. When she is asked to hold her right arm abducted at 45°, then laterally rotate her forearm against resistance, she is unable to do so.

What is the most likely diagnosis? Pain and weakness The subacromial bursa may be involved  Pain at the middle of the upper arm The tentative diagnosis  Rotator cuff tear Differential diagnosis  Rotator cuff tendonitis  Pain without weakness  A nerve injury  Weakness without pain

The tendons of which two muscles are most likely involved? Supraspinatus Infraspinatus

What events commonly precipitate such an injury? Rare in patients < 40 years old except in young athletes Common in patients > 50 years with shoulder pain Other common causes:  Direct blow to the affected shoulder  Falling onto an outstretched hand  History of recurrent rotator cuff tendonitis  Lifting a heavy object  Shoulder dislocation

What are the innervations and actions of these muscles? Supraspinatus  Suprascapular n. (C4-C6)  abduction of the arm beyond the initial 20° Infraspinatus  Suprascapular n. (C4-C6)  External rotation of the arm Teres minor  Axillary n.  Help in external rotation of the arm Subscapularis  Upper and lower subscapular n. (C5-7)  Help in median rotation and adduction of the arm

Reference First AID CASES for the USMLE STEP1  Mc Graw Hill  Tao Le, Kendall Krause, Joshua P. Klein, Anil Shivaram